Some mobile terminal apparatuses such as a smartphone, a mobile PC (Personal Computer) and a tablet terminal are provided with a video output terminal of a High-Definition Multimedia Interface (HDMI: registered trademark, the same hereinafter) specification or a Mobile High-definition Link (MHL: registered trademark, the same hereinafter) specification, and configured so as to be able to output an image (still image or moving image) to an external display apparatus via the terminal, that is, to function as a source device.
Moreover, such a mobile terminal apparatus detects a vertical direction (vertical direction of a display screen) of the apparatus by an embedded sensor, and performs control to rotate an image that is displayed on a display screen 90° according to a change in the detection result, thereby a vertical direction of the image when viewed from a user is fixed at all times.
Thus, basically, two screen configurations of portrait and landscape exist in such a mobile terminal apparatus. However, since the HDMI specification and the MHL specification are specifications premising a landscape output image as a format having a size of 1280×720 pixels, an aspect ratio of 16:9 and the like, a landscape image is provided at all times at a time of image output in a mobile terminal apparatus that employs these specifications. Note that, even an HDMI adapter compatible with a wireless specification Miracast premises that an output image is landscape in the same manner. Accordingly, a landscape image is output as it is and a portrait image is output after being added with black band parts on right and left to an external display apparatus.
Moreover, Japanese Laid-Open Patent Publication No. 2005-221634 discloses a technology that in an image display apparatus provided with a storage portion that stores image data and processing conditions including a processing size of the image data, information of a type, a size, and an aspect ratio of the image data is acquired from the storage portion, whether or not the acquired size matches the above-described processing size is judged, and when the both do not match, the image data is subjected to processing under the above-described processing conditions.
However, since a size and an aspect ratio of an image that is transferred with the HDMI specification or the MHL specification from a mobile terminal apparatus are fixed to be landscape, in a conventional display apparatuses including the image display apparatus described in Japanese Laid-Open Patent Publication No. 2005-221634, an orientation of an image received by the display apparatus is unclear and it is impossible to perform judgment such as whether to rotate the image and whether to add black band parts on a display apparatus side. Accordingly, a mechanism with the HDMI specification or the MHL specification expanded is desired for such judgment.
Further, black band parts are sometimes added to an output image from the mobile terminal apparatus, and even when display with the black band parts removed as unnecessary parts is desired in the display apparatus, there is no information showing whether to be the output image with the black band parts added or the output image without addition on the display apparatus side, thus making it also impossible to remove them automatically.
Furthermore, when an output image including black band parts, which is output from the mobile terminal apparatus, is displayed on the display apparatus, there is no information showing which orientation an actual image of an output source (that is, an image in which the black band parts are removed from the output image) has on the display apparatus side. Thus, it comes into a state where a user has to change a seeing position (for example, the user is positioned horizontally to the display apparatus) to visually identify the actual image, so that it becomes necessary to operate the display apparatus for rotation, or a state where an entire display screen of the display apparatus is not able to be used to a maximum extent for displaying largely.
Furthermore, when the display apparatus is an apparatus with a touch sensor, such a using case is considered that not only an image is received from the mobile terminal apparatus serving as a source device, but touch information received at the display apparatus is returned to the mobile terminal apparatus to control so that the mobile terminal apparatus is operated with the touch operation at the display apparatus. In this using case, if processing such as rotation and addition of black band parts is executed for an output image from the mobile terminal apparatus freely on the display apparatus side, a touch coordinate detected by the display apparatus is deviated from that of an output video of the mobile terminal apparatus, thus making it impossible to perform an operation correctly even if the touch information is returned to the mobile terminal apparatus as it is.
The above-described points can be caused in the same manner also when an image is output from a source device in which a size and an aspect ratio of an output image are fixed and the output image is displayed on the display apparatus without limitation to the HDMI specification or the MHL specification.